The road to the mythical kingdom of Westeros now passes through Boston, as a local video game company launches a new game based on the popular television series “Game of Thrones.”

Titled Game of Thrones Ascent, the game debuts Thursday on the Facebook social network. Fans of the HBO series can play as nobles in the service of the great families portrayed on the show. Facebook friends can join forces online to complete challenging tasks. Or they can compete for the wealth and status they’ll need to sway the destiny of the Seven Kingdoms.

But Disruptor Beam Inc., the small Boston game development house that has built Game of Thrones Ascent, faces a more arduous task. It must find an audience for a new online game, even as the growth of social gaming has begun to ebb.

Facebook reported no growth in its gaming revenue during the fourth quarter of 2012. Zynga Inc., the San Francisco company that dominated Facebook gaming with titles like FarmVille and Words With Friends, lost $209 million last year.

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Jon Radoff, Disruptor Beam’s founder and chief executive, said his game’s deeper, more sophisticated content will attract gamers who have grown bored with simpler fare. “You’ve got these moral shades of gray, you’ve got the complexity of human interaction, and that’s what we were interested in bringing to life in a game,“ Radoff said.

While the TV series features assassinations, duels, and major battles, the Facebook edition is all about strategy. “You’re not going to put a sword in your hand and wave it around and start hacking at stuff,” said Radoff. Instead, “it’s closer to a board game.” Players hire virtual soldiers, build castles, and go on quests in search of treasure, all with an eye to becoming the highest-ranking noble in the land.

“There’s so much in the game for people to do and so much to explore,” said Hank Howie,
a Boston video game industry veteran who is Disruptor Beam’s chief operating officer. In all, said Howie, a player can attempt over 1,000 different quests while playing the game. Over time, new challenges will be added to keep the game fresh.

Disruptor Beam Inc.

Facebook members will be able to choose to purchase special abilities and tools.

Facebook members will be able to play the game for free. But as with many Facebook games, they can choose to purchase special abilities and tools that make the experience easier and more entertaining.

Radoff said that game items will cost anywhere from 10 cents to $20. But gamers will be able to play the entire game without spending a cent.

Simply winning the right to build the game was a major coup for Radoff’s small company.

The industry is dominated by giant companies like Electronic Arts Inc. and Activision Blizzard Inc., which often deploy hundreds of programmers, artists, and writers to create a single game. In addition, HBO’s parent company, Time Warner Inc., operates a video game business of its own.

But Radoff came up with his own proposal for a Facebook game set in Westeros. Then he successfully pitched it to George R. R. Martin, the novelist whose best-selling books inspired the TV series.

Martin was unavailable to be interviewed, but in a blog posting last May he praised the early work on the game. “Jon and his designers took great pains to make sure the flavor of the novels is here,” he wrote.

Or at least most of the flavor. The books and TV show feature brutal violence and explicit sex; not so the Facebook version. “We geared it toward a PG-13 type of rating,” said Radoff.

Still, none of it will matter if Game of Thrones Ascent fails to attract a lot of players. “If you don’t generate enough critical mass of both paying and nonpaying users, the game doesn’t really get off the ground,” said industry analyst Brett Sappington of Parks Associates in Dallas. “If there are not many other players, it’s not very interesting.”

But Sappington said Disruptor Beam’s new game has a good chance of success. Despite the slowdown in Facebook gaming, tens of millions continue to play. Besides, he added, the “Game of Thrones” franchise “is a very hot property right now.”

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